Stock-Based Compensation - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
	Jan. 27, 2021	Sep. 30, 2021	Dec. 31, 2020
Equity Incentive Plan
Number of Options
Beginning balance (in shares)		30,488,300
Granted (in shares)		5,287,031
Exercised (in shares)		(2,695,995)
Cancelled/forfeited (in shares)		(941,576)
Ending balance (in shares)		32,137,760	30,488,300
Weighted Average Exercise Price
Options outstanding, beginning of period, weighted average exercise price (in dollars per share)		$ 2.45
Granted (in dollars per share)		4.74
Exercised (in dollars per share)		2.30
Cancelled/forfeited (in dollars per share)		3.52
Options outstanding, end of period, weighted average exercise price (in dollars per share)		$ 2.82	$ 2.45
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, outstanding		8 years 3 days	8 years 9 months
Aggregate intrinsic value, outstanding		$ 213,995	$ 885
STI Plan
Number of Options
Beginning balance (in shares)		6,490,208
Granted (in shares)	399,553	5,516,399
Exercised (in shares)		(1,630,925)
Cancelled/forfeited (in shares)		(846,200)
Ending balance (in shares)		9,529,482	6,490,208
Weighted Average Exercise Price
Options outstanding, beginning of period, weighted average exercise price (in dollars per share)		$ 2.49
Granted (in dollars per share)	$ 2.767	7.82
Exercised (in dollars per share)		2.54
Cancelled/forfeited (in dollars per share)		2.67
Options outstanding, end of period, weighted average exercise price (in dollars per share)		$ 5.55	$ 2.49
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, outstanding		8 years 3 months 7 days	9 years 3 months 3 days
Aggregate intrinsic value, outstanding		$ 39,171	$ 1,174